High resolution acoustic pulse-echo ranging system

Abstract

The uncertainty inherent in high-resolution acoustic pulse-echo distance measuring systems which depend on threshold detection is overcome by transmitting a multi-cycle shot of acoustic energy having a sharply peaked amplitude profile, and locating the peak amplitude of a received echo. The peaked amplitude is achieved by timing the duration of energization of a transducer producing the shot so that energization is terminated before the amplitude of oscillation of the transducer has reached a maximum. This produces a shot which has a definite largest cycle, which should in turn produce an echo having a definite largest cycle.

I claim: 
     
       1. In an acoustic pulse-echo ranging system comprising a transducer assembly, a transmitter supplying plural cycles of high frequency electrical energy to the transducer assembly to cause it to emit a shot of high frequency acoustic energy, a receiver receiving electrical signals generated by said transducer responsive to an echo formed by acoustic energy reflected back to said transducer by a target surface, and a counter counting an elapsed time between emission of said shot and receipt of said echo, the improvement wherein the transducer assembly has a sufficient quality factor that high frequency electrical energy must be applied to it for more than a plural first number of complete cycles before the amplitude of the emitted shot of acoustic energy has reached a maximum, the transmitter is configured supplying a plural number of complete cycles to the transducer assembly which is no greater than said first plural number, and the receiver is configured to detect that individual cycle of the received echo which has the maximum amplitude.   
     
     
       2. An acoustic pulse-echo ranging system according to claim 1, wherein the receiver includes a tracking peak detector. 
     
     
       3. An acoustic pulse-echo ranging system according to claim 2, wherein the receiver further includes a rate amplifier receiving the output of the tracking peak detector. 
     
     
       4. An acoustic pulse-echo ranging system according to claim 2, wherein the receiver includes an automatic gain controlled amplifier and a bandpass filter preceding the detector, and the detector is responsive only to signals exceeding a threshold amplitude. 
     
     
       5. A method of operating an acoustic pulse-echo ranging system comprising electrically energizing and electro-acoustic transducer with plural cycles of high-frequency electrical energy to cause it to transmit a multi-cycle shot of acoustic energy having an amplitude profile which is sufficiently sharply peaked that there is no ambiguity as to which cycle of the shot has a highest amplitude, and determining the temporal location of a peak amplitude of an echo of said shot received by said transducer in order to range a target producing said echo, wherein the duration of energization of the transducer producing the shot is timed to terminate energization before the amplitude of oscillation of the transducer has reached a maximum amplitude attainable response to a level of energization applied to the transducer.